Back to Search Start Over

Spatial and temporal distributions of terrestrial and marine organic matter in the surface sediments of the Yangtze River estuary.

Authors :
Zhang, Shanshan
Liang, Cui
Xian, Weiwei
Source :
Continental Shelf Research. Dec2020, Vol. 203, pN.PAG-N.PAG. 1p.
Publication Year :
2020

Abstract

Riverine supply of largely terrestrial carbon is important to the carbon cycle chemistry of the oceans. Along a river-ocean continuum, sedimentary organic matter composition and distribution can provide insights to the balance of terrestrial input and in situ production of an estuary. In the Yangtze River estuary (YRE), this balance is especially important to understand as human impacts and climate change continue to modify processes along the continuum. Here we discuss the sources and spatio-temporal distributions of organic matter in the coastal ocean surface sediments and how environmental factors have affected changes there. The isotopic compositions (δ13C and δ15N), total organic carbon (TOC), and total nitrogen (TN) of surface sediments were investigated along with sediment grain size and bottom water temperature, salinity, and total suspended matter. Evidence suggests that fine sedimentary grain size, bottom water temperature, and the circulation dynamics of water masses such as Changjiang Diluted Water (CDW) and Taiwan Warm Current (TWC) were the main factors affecting spatial and temporal distributions, with organic matter concentrations in autumn showing higher than that in spring and nearshore areas higher than offshore. An isotopic-based two end-member mixing model suggests that terrigenous inputs were the main source (about 53%) of organic matter in the YRE, followed by autochthonous marine organic matter, in both seasons. Terrestrial organic matter distribution, controlled by the CDW, decreased seaward from the mouth, as expected, and the proportion of terrestrial organic carbon increased in autumn compared to spring. Intrusions of the TWC water likely contributed to the increase of marine components in a tongue-shaped area during both seasons. • Spatial changes in TOC and TN were significant differences in spring and autumn. • High values of sedimentary organic carbon and nitrogen were observed in autumn. • Terrigenous inputs were the main source of organic matter in the continuum in both seasons. • TOC and TN correlated best with fine sedimentary grain size, and the CDW also explained variations in their distribution. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
02784343
Volume :
203
Database :
Academic Search Index
Journal :
Continental Shelf Research
Publication Type :
Academic Journal
Accession number :
143800656
Full Text :
https://doi.org/10.1016/j.csr.2020.104158